Perfluoroalkylethoxylate having the following structure are known: EQU R.sub.f --(CH.sub.2).sub.x --(OCH.sub.2 CH.sub.2).sub.y --OR
wherein R.sub.f is one or more perfluoroalkyl groups having between 2 and 30 carbon atoms: x is 1 to 3; y is 1 to 200; and R is hydrogen, alkyl or aryl. They can be prepared by the reaction of one or more pefluoroalkyl alkanols with ethylene oxide in the presence of a catalyst. They have several important industrial applications, including use as nonionic fluorosurfactants in the manufacture of PVC films, electrochemical cells, and photographic coatings. The useful properties of such fluoroalkylethoxylates are strongly influenced by their structural features, e.g. the size and chemical structure of the R.sub.f group, whether the composition comprises molecules having R.sub.f groups of the same length or a mixture of molecules having R.sub.f groups of different lengths, and the average number (y) and distribution of oxyalkylene groups. Fluoroalkylethoxylate compositions comprising a mixture of molecules having linear perfluoroalkyl groups of different length (for example, the commercial product ZONY.RTM. FSN marketed by E. I. du Pont de Nemours and Company) have distinctive surfactant properties, and can be considerably less expensive to manufacture than single isomer analogs. Unfortunately, such known mixtures of fluoroalkylethoxylates suffer from several deficiencies, including solubility in water of less than 10 weight percent and the tendency to form solutions containing sediment. (The term "solubility" as used in this specification is defined as the weight percent of fluoroalkylalkoxylate which may be added to a solvent such as water, or a water-organic solvent mixture at 25.degree. C. without causing the formation of turbidity or sediment).
It is more convenient and economical to manufacture, store, and ship fluoroalkylalkoxylate in a solution of higher concentration, typically at about 40 percent by weight. In order to achieve this high solution concentration, known fluoroalkylalkoxylates must be dissolved in an organic solvent, such as isopropyl alcohol (IPA), or in a solvent mixture comprising water in combination with one or more of such organic solvents. However, the resulting solution may be flammable or have increased toxicity, and thus be more difficult and expensive to ship and use safely. In addition, the users of said fluoroalkylalkoxylate solutions frequently must remove the organic solvent during their manufacturing operations; this can be expensive and result in increased worker safety and environmental hazards. Even when dissolved in organic solvent mixtures, known fluoroalkylalkoxylates tend to form sediments. Such sediments are not easily filterable, and they tend to form continuously over time, which makes it impractical to remove the sediments from fluoroalkylalkoxylate solutions before shipment to the user. There are other fluoroalkylalkoxylates disclosed in the prior art which have higher water solubility, e.g. those having a large average number of the hydrophilic oxyalkylene groups, typically greater than about 18 such groups. Another example is Fluorotenside FT 219 marketed by Bayer AG; however, the structures of that product and related compositions incorporate additional hydrophilic functional groups, such as sulfonylamido linkages. In addition, a high degree of alkoxylation may result in the fluoroalkylalkoxylate composition forming a gel during preparation that makes them difficult or impossible to use.
A fluoroalkylalkoxylate having good nonionic surfactant properties and capable of being supplied in water solution at concentrations of at least 40 percent by weight without the formation of sediment would have great utility and value in the marketplace.